1. Field of the Invention
This invention relates to a clamp lift truck which is capable of clamping four sides of goods which are stacked in the form of a rectangular hexahedron.
2. Description of Prior Art
Pallets are widely used for handling hexahedral stacks of goods, for example, for transhipping or transferring carton boxes of cleansers, foods, medicines and the like. With the propagation of racked storehouses which reduce the space of storage and facilitate the load handling, it has become the general practice to use selectively two types of pallets, namely, ordinary pallets which are used for transportation of goods and rack pallets which are used for storage of goods. The ordinary pallet used for the transportation consists of a low platform which has a plural number of flat plates tightly fixed on upper and lower sides of a number of parallel ribs for distributing as much as possible the load of goods which are stacked thereon in multiple layers. On the other hand, with the rack pallet which is not intended for stacking operation, it is not required to consider the distribution of load but it is necessary to provide a pallet construction which is suitable for automatic travel along rails, the rack pallet normally having a smaller number of plates on the underside thereof.
Therefore, when shipping out goods which have been stored in a racked storehouse, there arises a necessity for replacing pallets. In this connection, the most rational and prompt pallet replacing method is to clamp and lift each stack of goods above the pallet to a height suitable for its replacement.
As for the means for clamping a stack of load, there has been used a side clamp lift 1 which is provided with a pair of clamp plates 3 for clamping opposite sides of a stack 2 of encased goods of rectangular hexahedral shape, as shown in FIG. 1 of the accompanying drawings. However, this type of side clamp lift has a difficulty depending upon the dimensions of unit casing or each carton box of rectangular hexahedral shape as explained hereafter with reference to FIG. 2. In order to stack a maximum number of cases each having a width a, a depth b and a given height on a square pallet having sides of l in length, they are stacked in a mosaic fashion as shown in FIG. 2 for preventing them from easily breaking loose. In this instance, unless 3a=b, a void space in the form of a square column having sides of a length h is necessarily formed at the center, and, especially in a case where h=l-2b&gt;a, stack portions C.sub.3 and C.sub.9 are left free of the reactions of the clamping force as applied on the opposite sides of the stack by the clamp plates acting in the arrowed directions I--I. If the stack is clamped in the directions of II--II, stack portions C.sub.6 and C.sub.12 are left unclamped and easily fall off when moved.
Similar problems occur also when loading and unloading stacked goods on a vehicle.